A large volume of trash, including leaves, twigs, plastic or paper cups, cigarette butts, and wrappers, and the like, pass into storm drains adjacent to paved surfaces such as streets and parking lots, such as through curb inlets.
Larger spills of oil can also flow into storm drains, such as from loading docks, gas stations, and the like. In addition, quantities of oil or other hydrocarbons are frequently spilled on the ground and subsequent water flow, such as from rain, can cause the oil to flow into storm drains. This is referred to as "non-point-source pollution."
The volume of oil from non-point-source pollution in typical water runoff is surprisingly large. For example, a government study in one published article showed that stormwater sampled from street sites contained an "event mean concentration" of 2.2 mg. of oil per liter of runoff water. Shepp, "Petroleum Hydrocarbon Concentrations Observed in Runoff from Discrete, Urbanized Automotive-Intensive Land Uses," Watershed '96. If one meter of rain per year falls on a street 10 meters wide, then at that observed mean rate, the annual runoff from each kilometer of street will contain about 275 liters of hydrocarbons. Moreover, other studies of non-point-source pollution have measured oil concentrations an order of magnitude higher at some locations. Spills can increase the volume of oil even more.
The result of such problems include enormous annual costs, both financial and environmental, by contaminating natural receiving waters.
Known systems typically use a screen-type filter through which the water runoff passes. However, such systems are prone to becoming clogged with debris, thereby blocking the inlet to the storm drain. Also, such systems can collect only limited quantities of oil.
There has been a need for some time for trash and oil recovery systems that would (1) contain oil quickly and permanently, (2) prevent inlets from being clogged with debris, and (3) to permit removal of trash and oil for disposal.
Accordingly, it is a primary object of the present invention to achieve a more effective system for recovering trash and oil from water passing into storm drains or the like.
It is another object of the invention to provide methods and apparatus for effectively containing oil spills flowing into storm drains, over a range of flow rates.
It is another object of the invention to provide methods and apparatus for ameliorating oil spills by entrapping the oil in an oil-sorbent material.
It is another object of the invention to provide a means of improving the collection of spilled oil.
It is another object of the invention to provide collection systems that do not cause debris clogs.
The present invention achieves the above and other objectives by use of a stormdrain insert with separate collection systems for trash and oil or other hydrocarbons. A tilted grate separates trash from oily inlet water and directs the trash to a separate basket, and the water flows through a corrugated, flexible canister containing a hydrophobic, compliant, oil-absorbent, copolymer material arranged in a number of bodies having high surface area. Preferably, the material is formed with a binder in a novel extrusion process. The inserts can be suspended in a storm drain adjacent to a curb inlet.
Other aspects of the invention will be appreciated by those skilled in the art after a reading of the detailed disclosure of the present invention below.